I am not receiving PTT calls, presence updates or contact list updates on my Android 6.0 device

Devices using Android M OS (Android 6.0) have battery optimization features that place apps in Doze mode to improve battery life. When devices are left unplugged, stationary and with the screen off for a period of time, they will enter Doze mode automatically. Doze mode disconnects the Bell Push to Talk (PTT) application from the network, which blocks incoming calls, presence updates or contact list updates.

To prevent this from happening, you can disable battery optimization. To do so:

1. From the Home screen, navigate: Apps > Settings > Battery.
2. Tap the Menu icon  (located in the upper-right).
3. Tap Battery optimization.
4. Tap the Not optimized dropdown menu (located at the top).
5. Tap All apps.
6. Tap Don’t optimize.